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Dual MAF wiring idea

1757 Views 8 Replies 5 Participants Last post by  theman
I am working on putting in dual MAFs and came up with this idea. Instead of connecting the wires together from each MAF (4 per sensor) and running each air signal wire from the MAFs to an SAFC to be summed, why not run the second MAF as a dummy unconnected. Then just run the air signal wire from the functioning MAF to each of the two SAFC inputs to be summed. Reliability should be a little better and fewer connections to make. Anyone think it will work properly?
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I don't see how that will help air flow threw the meter?
The way to do it is kinda like this:

Splice into power from existing MAF plug, run this to power input on second MAF.

Splice into ground from existing MAF plug, run this to ground input on second MAF.

Plug wire into output terminal of second MAF, run this to the blue wire on your S-AFC.

Set S-AFC to use both sensors and sum the inputs.

The other two wires on the second MAF are NOT needed. I don't think it can get much more simple than that.

Sure you can try your idea, but the amount of work involved in doing it right is so small why not just do it? The above would probably take about 30 minutes, and the cost is exactly the same. I'll all for innovation to make things work better, or do it cheaper (the whole idea of dual MAFs), but not to avoid a extra half hour of cutting wires. :D

That and the air flow in each MAF might not be perfectly matched. Using each input is a sure way to make sure you are measuring air properly.
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I might have not been too clear on my first post so I try to clarify. Consensus is to connect the power and grounds together and then send each air flow signal to the two inputs of the SAFC for summation.

Instead, I was wondering why not just send one air flow signal to both inputs of the SAFC for summation. Would end up looking like a Y.

Theoretically, if both sensors are functioning correctly, it shouldn't make a difference if the SAFC uses a signal from seperate MAFs or the signal from one. Just as long as you input a signal to both inputs of the SAFC to add them together.

I thought this would be a better idea since there would be no need to connect power and ground at all. And there would be no variance in signal from getting it from two difference MAFs. With one MAF functioning, less chance of one going bad and not knowing. The second MAF would just be sitting in the air intake path to allow for more volume to be drawn into the turbo. Air flow volumes should be identical and the air flow signal should be exactly doubled when summed.

So bottom line, the signal from one MAF would be input into both inputs on the SAFC. They get summed and the SAFC outputs the new signal to the ECU. What do you guys think? No need to connect the two MAFs togther electrically.
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Hey, it SHOULD work. Give it a try. If it doesn't, then hook the second one up.
Well then why run two MAFs at all? Using your theory you could just have a second pipe with nothing on it at all. Correct me if I'm wrong, but the whole point to wiring in two MAFs is so that even if there are slight differences in airflow through them for whatever reason the signals would be summed and accurately sent to the ECU, giving proper air signals to be matching with proper fuel.
In theory you could have a second pipe with nothing in it at all, but you would have to calculate how much metered air is flowing through the MAF vs. how much air is flowing through the pipe (going around the MAF) Then you would need to adjust the MAF signal to account for the additional un-metered air. I think it would be hard to have the work correctly in all cases though.

If you put a "dummy" MAF in the second pipe then the air flow through both pipes should be equal to 50% of the flow through the "working" MAF so if you just doubled this you would have the total amount of air flow.

Please keep in mind that I don't have dual MAF's, and have no first hand expeirance with a setup like this, but in theory I believe what I described would be true.
If you used a second pipe (ie MAF bypass tube) you would have to monitor fuel trims during closed loop to make sure the correct amount of air was going through each pipe. This is hard to do on an OBD1. Either that or you could use some sort of a flow tester to find out how the air would be divided up.

There is currently a discusing going about this on the list, I will post here if we reach some sort of an agreement.
Yeah you're right about having the dummy one in there to make the airflow the same, I guess I should've specified a pipe of the same inside diameter of the dummy MAF. If you have to make the second pipe anyway and you're not wiring it up, save the cost of the dummy MAF, I just didn't want to be long winded.
The dummy MAF will probably work, it has on other cars such as the stillen stuff for the 300zx but my point was that if you're going to have two MAFs to utilize the accuracy of precise messurement from both, since as was mentioned the wiring isn't difficult at all.
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